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Publication Series on Dangerous Substances (PGS 3)

Guidelines for quantitative risk assessment

Ministerie van VROM >

staat voor ruimte, wonen,milieu en rijksgebouwen.Beleid maken, uitvoerenen handhaven.

Nederland is klein.Denk groot.

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Preface

PREFACE

This report documents the methods to calculate the risks due to dangerous substances in the

Netherlands using the models and data available. Calculation of the risks relates, on the one hand,

to stationary installations and, on the other, to transport and related activities.

The report consists of two parts. Part 1, describing the methods to calculate the risks of

stationary installations, was written by the National Institute of Public Health and the

Environment (RIVM) under a supervisory committee of representatives from the subcommission

on Risk Evaluation of the Committee for the Prevention of Disasters (CPR-RE). Part 2, drawn

up under the responsibility of the Ministry of Transport, Public Works and Water Management,

describes the calculation of the risks connected with the transport of dangerous goods, based on

the approach developed in accordance with the Ministry of Housing, Spatial Planning and the

Environment and set down in the last few years in various commissions.

Although the report describes the present-day calculation methods (in practice, no better

methods are currently available), discussions on a number of subjects in the supervisory

committee led to the conclusion that additional research would be necessary to guarantee the

quality of the calculation methods in the future. Three subjects for study were indicated:

A. The failure frequencies of stationary installations. Failure frequencies are based on the so-

called COVO study from 1981. Additional failure frequencies have been determined in various

studies carried out for the Dutch government over the years. Recently, new studies have been

published, report ing different figures - mostly higher - for a number of failure frequencies. A

more detailed study on the failure frequencies will be carried out, concentrating especially on

the original data sources.

B. The meteorological model. Dispersion calculations are carried out as part of the risk analyses

using generally accepted meteorological models and the corresponding meteorological data.

The national model used in air pollution calculations has recently been adapted to include new

insights. At the moment, meteorological statistics are not sufficiently available to apply this

new meteorological model to risk analyses. The relevance of the new model to risk analyses

should be ascertained; furthermore, the consequences which the new model, including themodel parameters, could have on the results of calculating risks should be examined. The study

on these consequences will be started up in the short term.

C. Differences in risk calculations for transport and for stationary installations. The method to

calculate the risks of transporting dangerous goods is comparable to the calculation method

applied to stationary installations. During the last few years, the basic principles of risk

analysis have been discussed and established with the parties involved. Since developments in

the risk calculation methods for transport and stationary installations were separate, several

differences exist between the basic principles in risk calculations for transport and for

stationary installations. These differences relate, among other aspects, to the frequency ofcatastrophic failure of tank wagons relative to stationary tanks and to certain loss of

containment scenarios.

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Preface

The Committee for the Prevention of Disasters considers it important to have reliable risk

calculations for stationary installations and for transport of dangerous goods; these should, as far

as possible, also be founded on similar basic principles. It is therefore advisable to analyse the

basic principles of the calculation methods and to study the consequences of removing the

differences in the calculation methods. Both the Ministries mentioned above can then decide

whether these differences should actually be reduced.

The discussions show that the methods of risk analysis are still being further developed. The

Committee for the Prevention of Disasters is p leased that with the publication of this report a

substantial contribution will be made to the further development of this risk analysis instrument.

The Committee thanks the government experts, research institutes and industry for their

contributions. The Committee for the Prevention of Disasters is convinced that the report will

be of great value for all those dealing with risk analysis and risk management.

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Table of Contents 0.1

TABLE OF CONTENTS

1. INTRODUCTION

2. SELECTION OF THE INSTALLATIONS FOR THE QRA

2.1 INTRODUCTION.................................................................................................................................................................................2.1

2.2 EXCLUSION OF PARTICULAR SUBSTANCES.............................................................................................................................2.2

2.3 THE SELECTION METHOD..............................................................................................................................................................2.2

2.3.1 Definition of installat ions in an establishment ......................................................................................2.4

2.3.2 Calculation of the indicat ion number, A.....................................................................................................2.4

2.3.3 Calculation of the selection number, S......................................................................................................2.10

2.3.4 Selection of installations......................................................................................................................................2.11

2.3.5 Specific problems .....................................................................................................................................................2.11

APPENDIX2.A PROCEDURE TO ASSESS THE OBLIGATION TO MAKE A SAFETY REPORT...........................................2.15

APPENDIX2.B AN EXAMPLE CALCULATION............................................................................................................................2.22

APPENDIX2.C COMMENTARY......................................................................................................................................................2.28

3. LOSS OF CONTAINMENT EVENTS

3.1 INTRODUCTION.................................................................................................................................................................................3.1

3.2 LOSS OF CONTAINMENT EVENTS AT ESTABLISHMENTS......................................................................................................3.1

3.2.1 Stationary pressurised tanks and vessels ..................................................................................................3.2

3.2.2 Stationary atmospheric tanks and vessels ................................................................................................3.4

3.2.3 Pip es......................................................................................................................................................................................3.7

3.2.4 Pump s..................................................................................................................................................................................3.8

3.2.5 Heat exchangers.............................................................................................................................................................3.9

3.2.6 Pressure relief devices ...........................................................................................................................................3.10

3.2.7 LOCs for storage in warehouses ...................................................................................................................3.11

3.2.8 Storage of exp losives..............................................................................................................................................3.11

3.2.9 Transport units in an establishment...........................................................................................................3.12

APPENDIX3.A COMMENTARY......................................................................................................................................................3.17

4. MODELLING SOURCE TERM AND DISPERSION4.1 INTRODUCTION.................................................................................................................................................................................4.1

4.2 PROPERTIES OF SUBSTANCES ......................................................................................................................................................4.2

4.3 OUTFLOW MODELS..........................................................................................................................................................................4.2

4.4 REPRESSION FACTORS ...................................................................................................................................................................4.5

4.4.1 Blocking systems.........................................................................................................................................................4.5

4.4.2 Other rep ression systems.....................................................................................................................................4.6

4.5 POOL EVAPORATION........................................................................................................................................................................4.6

4.6 VAPOUR CLOUD DISPERSION.......................................................................................................................................................4.7

4.6.1 Coupling out flow and vapour cloud dispersion...................................................................................4.7

4.6.2 Modelling the vapour cloud dispersion...................................................................................................4.104.6.3 Release inside a building......................................................................................................................................4.11

4.6.4 Fires and plume rise................................................................................................................................................4.13

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Table of Contents 0.2

4.7 IGNITION4.13

4.7.1 Direct ignition..............................................................................................................................................................4.13

4.7.2 Delay ed ignit ion.........................................................................................................................................................4.15

4.7.3 Substances both toxic and flammable ........................................................................................................4.15

4.8 EFFECTS OF IGNITION OF A VAPOUR CLOUD........................................................................................................................4.16

4.9 RUPTURE OF VESSELS..................................................................................................................................................................4.16

4.10 M ETEOROLOGICAL DATA........................................................................................................................................................4.17

APPENDIX4.A M ODEL TO CALCULATE THE PROBABILITY OF DELAYED IGNITION...................................................4.19

APPENDIX4.B M ETEOROLOGICAL DATA.................................................................................................................................4.21


5. MODELLING EXPOSURE AND DAMAGE

5.1 INTRODUCTION.................................................................................................................................................................................5.1

5.2 DAMAGE MODELLING....................................................................................................................................................................5.1

5.2.1 Probit funct ions ............................................................................................................................................................5.1

5.2.2 Toxic exp osure...............................................................................................................................................................5.3

5.2.3 Fire..........................................................................................................................................................................................5.6

5.2.4 Pressure effects for a vapour cloud explosion.......................................................................................5.8

5.3 POPULATION.......................................................................................................................................................................................5.8

5.3.1 Survey of the populat ion present ...................................................................................................................5.8

5.3.2 Fraction indoors and outdoors........................................................................................................................5.10

APPENDIX5.A COMMENTARY......................................................................................................................................................5.11

6. CALCULATION AND PRESENTATION OF RESULTS

6.1 INTRODUCTION.................................................................................................................................................................................6.1

6.2 CALCULATION OF THE INDIVIDUAL RISK AND THE SOCIETAL RISK................................................................................6.1

6.2.1 Definit ion of the grid.................................................................................................................................................6.1

6.2.2 Individual Risk calculat ion....................................................................................................................................6.2

6.2.3 Societal Risk calculation.........................................................................................................................................6.4

6.2.4 Definition of ignition event s for flammable substances..................................................................6.6

6.2.5 Probability of death, Pd, and fraction of deaths, Fd, for toxic substances....................6.10

6.2.6 Probability of death, Pd, and fraction of deaths, Fd, for flammables................................6.13

6.3 PRESENTATION OF THE RESULTS

..............................................................................................................................................6.16APPENDIX6.A PROBABILITY THAT THE GRID POINT IS COVERED BY THE CLOUD, PCI............................................6.18

APPENDIX6.B SAMPLE CALCULATION OF THE INDIVIDUAL RISK AT A GRID POINT..................................................6.21


7. QUANTITATIVE ENVIRONMENTAL RISK ANALYSIS

8. THE USE OF NEW MODELS IN A QRA

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Introduction 1.1

1. INTRODUCTION

A Quantitative Risk Assessment (QRA) is a valuable tool for determining the risk of the use,

handling, transport and storage of dangerous substances. QRAs are used to demonstrate the riskcaused by the activity and to provide the competent authorities with relevant information to

enable decisions on the acceptability of risk related to developments on site, or around the

establishment or transport route.

If the results of a QRA in the decision-making process are to be used, they must be verifiable,

reproducible and comparable. These requirements necessitate QRAs made on the basis of similar

starting-points, models and basic data. Ideally, differences in QRA results should only arise from

differences in process- and site-sp ecific information. A number of documents for attaining

comparability in the QRA calculations have been published over the years. The Committee for

the Prevention of Disasters (CPR) has issued three reports describing the methods to be used in a

QRA calculation, namely the Red Book, the Yellow Book and the Green Book. The RedBook, describing the methods for determining and processing probabilities, is to be used to

derive scenarios leading to a loss of containment event [CPR12E]. The Yellow Book describes

the models to determine the outflow and dispersion of dangerous substances in the environment

[CPR14, CPR14E], and finally, the Green Book describes the impact on humans of exposure to

toxic substances , heat radiation and overpressure [CPR16].

All three books provide the scientific information to be used in a QRA on the basis of present-

day knowledge. However, this information is not sufficient to carry out a complete QRA

calculation. Addit ional information is needed, for example, information related to policy

decisions and data for which adequate scientific knowledge is not available (yet). Usually,

standard values for this type of data are set by consensus following discussions between

representatives from industry, the competent authorities and the central government. The

outcome of these discussions has been published in a number of documents (e.g.[KO 9, KO 12,

KO 20-2, KO 24-2, IPO]). However, the large collection of documents issued over the years,

with documents sometimes sup erseding one another, has called up a need to merge them all into

one report, making use of experiences gathered in conducting QRA analyses. The outcome then is

this report, Guideline for Quantitative Risk Assessment, in which all necessary starting-points

and data needed to perform a QRA calculation are recorded.

The report is organized in the same way that a QRA calculation is performed, i.e. starting with

the selection of installations and the definition of loss of containment events, followed bydispersion and effect calculations, and the presentation of the results.

The selection of installations is described in Chapter 2. Since the total number of installations in

an establishment can be very large and not all installations contribute significantly to the risk, it is

not worthwhile to include all installations in the QRA. Therefore a selection method is given to

indicate the installations that contribute most to the risk.

The loss of containment events are defined in Chapter 3. Generic loss of containment events and

failure frequencies are defined for a number of standard installations like storage tanks, transport

units, pipelines and loading equipment. Normally, generic values should be used in the QRA

calculation; however, it is possible to use site-specific information so as to modify loss ofcontainment events and failure frequencies.

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Selection of installations 2.3

Figure 2.1 Outline of the selection method.

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1. The establishment is divided into a number of independent installations, according to the

procedure given in Section 2.3.1.

2. For all other installations, the intrinsic hazard, induced from the amount of substancepresent, the process conditions and the dangerous properties of the substance, is

determined. The indication number, A, shows the measure of intrinsic hazard of the

installation. This number is calculated according to the procedure given in Section 2.3.2.

3. The hazard of an installation is calculated for a number of points in the surroundings of the

establishment. The hazard at a point is induced knowing the indication number and the

distance between the point and the installation. The measure of the hazard at a given point

is indicated by the selection number, S, which is calculated according to the procedure given

in Section 2.3.3.

4. Installations are selected for analysis in the QRA on the basis of the relative magnitude ofthe selection number according to the procedure outlined in Section 2.3.4.

2.3.1 Definition of installations in an establishment

The first step in the selection method is to divide an establishment into a number of separate

installations. This is a complex process, which may be open for discussion. This section offers

some guidance.

An important criterion for the definition of a separate installation is that loss of containment of

one installation does not lead to release of significant amounts of substances from other

installations. Consequently, two installations are considered separate if they can be isolated in a

very short time following an accident.

Two different ty pes of installations are distinguished, i.e. process installations and storage

installations. A process installation can consist of several tanks, pipes and similar equipment. A

storage installation, like a storage tank, is always considered to be separate. Often a storage

installation is equipp ed with devices like recirculation sy stems and heat exchangers to keep the

substance at storage conditions. However, the installation is still considered as a storage

installation, whether or not such devices are present. The classification of transport units in an

establishment is described in Section 2.3.5.

Since the division into separate installations is a complex process, consultation between the

operator of the establishment and the competent authority is considered useful.

2.3.2 Calculation of the indication number, A

The intrinsic hazard of an installation depends on the amount of substance present, the physical

and toxic properties of the substance and the specific process conditions. The indication number,

A, is calculated as a measure of the intrinsic hazard of an installation.

The indication number, A, for an installation is a dimensionless number defined as:

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O3 a factor to account for the amount of substance in the vapour phase after release, based on

the process temperature, the atmospheric boiling point, the substance phase and the

ambient temperature.

The factors for the process conditions apply to toxic and flammable substances only. Forexplosives, O1= O2= O3= 1.

2.3.2.2.1 Factor O1

Factor O1(see Table 2.1) accounts for the type of installation, be it for processing or storage.

Table 2.1 Factor O1to account for the type of installation

Type O1installation for processing 1

installation for storage 0.1

2.3.2.2.2 Factor O2

Factor O2(see Table 2.2) accounts for the positioning of the installation and the presence of

provisions to p revent the substances disseminating into the environment.

Table 2.2 Factor O2to account for the positioning of the installation

Positioning O2

outdoor installation 1.0

enclosed installation 0.1

installation situated in a bund and a process temperature, Tp,

less than the atmospheric boiling point Tbpplus 5 C, i.e. Tp"Tbp+ 5 C

0.1

installation situated in a bund and a process temperature, Tp,

more than the atmospheric boiling point Tbpplus 5 C, i.e. Tp> Tbp+ 5

1.0

Notes:

1. For storage, the process temperature should be seen as the storage temperature.

2. The enclosure of the installation should prevent substances being spread in the

environment. This means that (a) the enclosure should remain unimpaired following the

physical pressures due to the instantaneous release of the installation inventory and (b) the

enclosure should reduce significantly the direct release into the atmosphere. A guideline: if

the enclosure reduces the source term into the atmosphere by more than a factor 5, or if the

enclosure redirects the release to a safe outlet, the inst allation will be considered enclosed,otherwise it is an outdoor installation.

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Table 2.4 Added value#accounts for liquid pool evaporation

#

$25 C "Tbp 0$75 C "Tbp< $25 C 1

$125 C "Tbp< $75 C 2

Tbp< $125 C 3

A 10% point should be used for mixtures of dangerous substances, i.e. the temperature at

which 10% of the mixture is distilled off.

6. For dangerous substances in non-dangerous solvents, the partial vapour pressure of the

dangerous substance at process temperature is to be used for the saturation pressure at

process temperature. The factor X increases linearly from 1 to 10 if the partial vapour

pressure of the dangerous substance at p rocess temperature increases from 1 to 3 bar.

7. The factor O3is limited to a minimum value of 0.1 and a maximum value of 10.

2.3.2.3 Limit value, G

The limit value, G, is a measure of the dangerous properties of the substance based on both the

physical properties and the toxic/explosive/flammable prop erties of the substance.

2.3.2.3.1 Limit value for toxic substances

The limit value for toxic substances (see Table 2.5) is determined by the lethal concentration,

LC50(rat, inh, 1h) and the phase at 25 C.

Notes:

1. The phase of the substance (gas, liquid and solid) assumes a temperature of 25 C. In

addition, the following subdivision holds for liquids:

Liquid (L) atmospheric boiling point Tbpbetween 25 C and 50 C

Liquid (M) atmospheric boiling point Tbpbetween 50 C and 100 C

Liquid (H) atmospheric boiling point Tbpabove 100 C

2. LC50(rat, inh, 1h) is the LC50value for rats using an inhalation method for exposure of one

hour. These values are listed for a number of toxic substances in the database [RIVM99].

3. The limit value should be derived from Table 2.5. Limit values to determine the Report on

Occupational Safety compliance are listed for a number of substances in [SZW97] and

[RIVM99]. These values can differ from those derived from Table 2.5 for some

carcinogenic substances and if new toxicity data are used.

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Table 2.5 Limit value, G, for toxic substances

LC50 (rat, inh, 1h) (mg m-3) Phase at 25 C Limit value (kg)

LC "100 gas 3

liquid (L) 10

liquid (M) 30

liquid (H) 100

solid 300

100 < LC "500 gas 30

liquid (L) 100

liquid (M) 300

liquid (H) 1000

solid 3000

500 < LC "2000 gas 300

liquid (L) 1000

liquid (M) 3000

liquid (H) 10,000

solid %

2000 < LC "20,000 gas 3000

liquid (L) 10,000

liquid (M) %

liquid (H) %

solid %

LC > 20,000 all phases %

2.3.2.4Limit value for flammable substances

The limit value for flammables is 10,000 kg.

Note:

1. Flammables are defined for the selection system as substances having a process

temperature equal to or higher than the flashpoint. The flashpoint is determined using the

apparatus of Abel-Pensky for flame points up to and including 65 0C and the app aratus of

Pensky-Martens for flame points higher than 65 0C.

2.3.2.5 Limit value for explosive substances

The limit value for explosive substances is the amount of substance (in kg) which releases an

amount of energy equivalent to 1000 kg TNT (explosion energy 4600 kJ/kg).

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2.3.2.6 Calculation of the indication number

The indication number, Ai, of an installation for a substance iis calculated as:

Ai= Q1 ! O1 ! O2 ! O3 (2.3)

Giwith:

Qi the quantity of substanceipresent in the installation (in kg)

O1 the factor for installation type, whether process or storage (-)

O2 the factor for the positioning of the installation, enclosed, bund or outdoors (-)

O3 the factor for the process conditions (-)

Gi the limit value of substancei(in kg).

For explosives, O1= O2= O3= 1 and, consequently, A = Q / G.

Various substances and process conditions can be present within one installation. In this case, an

indication number, Ai,p, is calculated for every substance, i,and for every process condition,p.

The indication number, A, for an installation is calculated as the sum over all indication numbers,

& i,pAi,p. This sum is calculated for three different groups of substances separately, namely,

flammables (AF), toxics (AT) and explosives (AE).

AT= & i,pAi,p, sum over all toxic substances and p rocess conditions

AF= & i,pAi,p, sum over all flammable substances and process conditions

AE= &i,p

Ai,p

, sum over all explosive substances and p rocess conditions

An installation can have up to three different indication numbers.

Note:

1. If a substance belongs to more than one group, an indication number is calculated for each

group separately. For instance, if a substance is both toxic and flammable, two indication

numbers, Ai,p, are calculated:

ATi,pfor the substance as a toxic using the total quantity, Q i, and the limit value, GT

i,

corresponding with the toxic properties.

AF

i,pfor the substance as a flammable using the total quantity, Qi, and the correspondinglimit value for flammables, GFi= 10,000 kg.

2.3.3 Calculation of the selection number, S

The selection number, S, is a measure of the hazard of an installation at a sp ecific location and is

calculated by multip lying the indication number, A, of an installation by a factor (100/L)2for

toxic substances and a factor (100/L)3for flammable or explosive substances. Again, three

different selection numbers can exist for one installation:

for toxics (2.4)

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for flammables (2.5)

for explosives (2.6)

L is the distance from the installation to the specific location in metres, with a minimum of

100 m.

The selection number has to be calculated for every installation at a minimum of eight locations

on the boundary of the establishment. The distance between two adjacent locations must not be

more than 50 metres. The selection number must be calculated for the total boundary of the

establishment, even if the establishment borders on a similar establishment. If the est ablishment

is bounded by surface water, the selection number must be calculated on the bank side situatedopp osite the establishment.

Besides the calculation on the boundary of the establishment, the selection number, S, must also

be calculated for every installation at a location in a residential area, existing or planned, closest to

the installation.

2.3.4 Selection of installations

An installation is selected for analysis in a QRA if:

the selection number of an installation is larger than one at a location on the boundary of the

establishment (or on the bank side situated opposite the establishment) and larger than

50% of the maximum selection number at that location.

or

the selection number of an installation is larger than one at a location in the residential area,

existing or planned, closest to the installation.

Note:

1. The effects of the release of toxic substances may extend further than the effects of the

release of flammable substances. If only installations with flammable substances are

selected and the selection number of an installation with a toxic substance is in the same

order of magnitude as the maximum selection number, the installation with toxic substances

should also be included.

2.3.5 Specific problems

2.3.5.1Inter-unit pipelines

Large inter-unit p ipelines in an establishment can contribute considerably to the risk caused bythe establishment e.g.:

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inter-unit pipelines may be situated near the boundary of an establishment,

inter-unit pipelines may release large amounts of substances due to their own hold-up and

the feed from the upstream vessel, and

inter-unit pipelines may have large failure frequencies.

For the selection method, the quantity present is calculated as:

For pipelines containing liquids or pure gases, the quantity present is set equal to the

amount in the pipeline, with a length equal to 600 seconds multiplied by the velocity of the

liquid or gas in the pipeline.

For pipelines containing liquefied pressurized gases, the quantity present is a function of

the diameter of the pipeline and the substance. The quantity present is equal to the amount

present in a pipeline, with a length that is emptied after 600 seconds. For a number of

reference substances, the length of the pipeline emptied is given in Figure 1.2. For all other

substances, the length can be estimated using the physical properties of the substance,

particularly vapour pressure at 10 C, to select one of the curves in Figure 1.2.If the length of the pipeline calculated exceeds the actual length of the pipeline, the quantity

present is equal to the amount between two quick-closing blocking valves isolating the pipeline at

an incident. The time needed to close the two blocking valves is assumed to be so short that the

amount released when the blocking valves are open is small compared to the amount between the

two blocking valves. If not, t he amount between the two blocking valves should be corrected with

the mass released during the t ime the blocking valves are open. However, the quantity present

should not exceed the amount in the length of the pipeline equal to 600 seconds multiplied by the

velocity of the liquid or gas, or the length of the pipeline emptied after 600 sec (liquefied

pressurized gases).

The factors for the process conditions O1- O3apply. An inter-unit pipeline should be considered

as a process installation, O1= 1. The factors O2and O3are given in Table 2.2 and Table2.3. An

underground inter-unit pipeline is to be considered enclosed (O2= 0.1).

To calculate the selection number, various p oints on the pipeline should be considered for the

location of the total quantity present. The distance between two neighbouring points must be

equal to circa 50 metres.

To select pipelines for a QRA calculation, a division is made in pipelines included in the

establishments permit and pipelines not included. If an inter-unit pipeline is included in the

permit, the pipeline should be dealt with like all other installations. However, if an inter-unitpipeline is not included in the permit, the installations without these inter-unit pipelines are first

selected. This results in a list of installations in the establishment. Next, a new selection is made

to include the inter-unit pipelines not included in the permit. This results in an additional list of

inter-unit pipelines to be considered in the QRA.

If an inter-unit pipeline is selected on the basis of the selection number of one or more release

locations, the total inter-unit pipeline will have to be included in the QRA.

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Figure 2.2 Length of pipeline emptied after 600 s for a number of reference substances for a two

phase outflow at 10 C.

2.3.5.2 Loading and unloading activities

During loading and unloading activities, storage tanks are situated within the transport unit at the

establishment. Three installations have to be considered for the selection procedure, namely, the

storage tank in the transport unit, the loading facility and the connecting installation at the

establishment. The following rules apply:

the storage tank in the transport unit is considered a process installation if the time that

the transport unit is connected to a process installation is less than one day .In all other

cases, the storage tank in the transport unit is considered to be a storage installation.

the loading facility is a p rocess installation and should be included in the QRA if either the

supplying or the receiving installation is selected.

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Storage tanks on ships should be included if the presence of the ship is connected to the

establishment. Only the substances involved in loading and unloading activities have to be

considered for the selection. If a storage tank on a ship is to be considered, installations

without the storage tank on the ship are first selected. This results in a list of installationsof the establishment. Next, a new selection is made of installations with the storage tank on

the ships included. This results in an additional list of installations for consideration in the

QRA.

Transport units are only p resent part of the time. Although this is important in the QRA,

it is not considered in the selection procedure.

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Appendix 2.A Procedure to assess the obligation to make a Safety Report

2.A.1 Outline of the procedure

The procedure, outlined below, to determine whether a Safety Report should be obligatory was

taken up in the Council Directive 96/82/EC of 9 December 1996 on the control of major-accident

hazards involving dangerous substances [EU96]. It should be noted that the out line given here is

only a short description of the framework and should not be seen as the complete procedure. The

rules and notes in Annex I of the Council Directive 96/82/EC of 9 December 1996, taken up in

2.A.2, are decisive and should be considered carefully.

The procedure:

1. Determine the substances present in the establishment. Presence of substances is taken to

mean the actual or anticipated presence of such substances in the establishment, or thepresence of those substances believed to be possibly generated during a chemical process

which has got out of control.

Notes:

- If a substance is licensed, it is assumed to be present.

- The presence of a substance is meant to refer to a substance in the establishment for at

least five consecutive days or at a frequency of more than 10 times per year.

2. Determine for each substance,x,the maximum quantity present or likely to be present at

any one time, qx

.

Note:

- The licensed amount of substance is assumed to be present.

3. Look for the substancexin the table of Part 1 of Annex I

If substancexis named in the table of Part 1, determine the corresponding qualifying

quantity, Qx, in column 3 (Article 9).

If substancex is not named in the table of Part 1, determine in which category of the

table the substance falls. Determine the corresponding qualifying quantity, Qx, in

column 3 (Article 9).

4. Determine for each substancexthe value qx/ Qx. If qx/ Qx> 1 for one or more of the

substances, a Safety Report should be made.

5. If qx/ Qx< 1 for all substancesx, the sum q1/ Q1+ q2/ Q2+q3/ Q3+ .... has to be

calculated for two groups of substances separately, namely, for all substances classified in

the categories 1, 2 and 9, and for all substances classified in the categories 3, 4, 5, 6, 7a, 7b,

and 8. If one of the two sums is larger than 1, a Safety Report should be made.

Named substances should be classified and added accordingly to the categories in the table

of Part 2, using the qualifying quantity Qxof the table in Part 1.

There are databases available which give the classification of a number of dangerous substances,e.g. the database of substances of RIVM [RIVM99].

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2.A.2 Annex I of the Council Directive 96/82/EC of 9 December 1996

APPLICATION OF THE DIRECTIVE

INTRODUCTION

1. This Annex applies to the presence of dangerous substances at any establishment within the meaning ofArticle 3 of this Directive and determines the application of the relevant Articles thereof.

2. Mixtures and preparations shall be treated in the same way as pure substances provided they remain withinconcentration limits set according to their properties under the relevant Directives given in Part 2, Note 1, ortheir latest adaptation to technical progress, unless a percentage composition or other description isspecifically given.

3. The qualifying quantities set out below relate to each establishment.

4. The quantities to be considered for the application of the relevant Articles are the maximum quantities whichare present or are likely to be present at any one time. Dangerous substances present at an establishment only

in quantities equal to or less than 2 % of the relevant qualifying quantity shall be ignored for the purposes ofcalculating the total quantity present if their location within an establishment is such that it cannot act as aninitiator of a major accident elsewhere on the site.

5. The rules given in Part 2, Note 4, governing the addition of dangerous substances, or categories of dangeroussubstances, shall apply where appropriate.

PART 1

Named substances

Where a substance or group of substances listed in Part 1 also falls within a category of Part 2, the qualifyingquantities set out in Part 1 must be used.

Column 1 Column 2 Column 3

Qualifying quantity (tonnes)

Dangerous substances for the application of

Articles 6 and 7 Article 9

Ammonium nitrate 350 2500

Ammonium nitrate 1250 5000

Arsenic pentoxide, arsenic (V) acid and/or salts 1 2

Arsenic trioxide, arsenious (III) acid and/or salts 0,1

Bromine 20 100

Chlorine 10 25

Nickel compounds in inhalable powder form (nickelmonoxide, nickel dioxide, nickel sulphide, trinickeldisulphide, dinickel trioxide)

1

Ethyleneimine 10 20

Fluorine 10 20

Formaldehyde (concentration '90 %) 5 50

Hydrogen 5 50

Hydrogen chloride (liquefied gas) 25 250

Lead alkyls 5 50

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Dangerous substances for the application of


Liquefied extremely flammable gases (including LPG)and natural gas

50 200

Acetylene 5 50

Ethylene oxide 5 50

Propylene oxide 5 50

Methanol 500 5000

4, 4-Methylenebis (2-chloraniline) and/or salts, inpowder form

0.01

Methylisocyanate 0.15

Oxygen 200 2000

Toluene diisocyanate 10 100Carbonyl dichloride (phosgene) 0.3 0.75

Arsenic trihydride (arsine) 0.2 1

Phosphorus trihydride (phosphine) 0.2 1

Sulphur dichloride 1 1

Sulphur trioxide 15 75

Polychlorodibenzofurans andpolychlorodibenzodioxins (including TCDD),calculated in TCDD equivalent

0,001

The following CARCINOGENS:

4-Aminobiphenyl and/or its salts,

Benzidine and/or salts,

Bis (chloromethyl) ether,Chloromethyl methyl ether,

Dimethylcarbamoyl chloride,

Dimethylnitrosomine,

Hexamethylphosphoric triamide,

2-Naphtylamine and/or salts,

and 1,3 Propanesultone 4-nitrodiphenyl

0,001 0.001

Automotive petrol and other petroleum spirits 5000 50,000

NOTES

1. Ammonium nitrate (350 / 2500)

This applies to ammonium nitrate and ammonium nitrate compounds in which the nitrogen content as a resultof the ammonium nitrate is more than 28 % by weight (compounds other than those referred to in Note 2) and toaqueous ammonium nitrate solutions in which the concentration of ammonium nitrate is more than 90 % byweight.

2. Ammonium nitrate (1250/5000)

This applies to simple ammonium-nitrate based fertilizers which comply with Directive 80/876/EEC and tocomposite fertilizers in which the nitrogen content as a result of the ammonium nitrate is more than 28% inweight (a composite fertilizer contains ammonium nitrate with phosphate and/or potash).

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3. Polychlorodibenzofurans and polychlorodibenzodioxins

The quantities of polychlorodibenzofurans and polychlorodibenzodioxins are calculated using the followingfactors:

International Toxic Equivalent Factors (ITEF) for the congeners of concern (NATO/CCMS)

2,3,7,8-TCDD 1 2,3,7,8-TCDF 0.1

1,2,3,7,8-PeDD 0.5 2,3,4,7,8-PeCDF 0.5

1,2,3,7,8-PeCDF 0.05

1,2,3,4,7,8-HxCDD 0.1

1,2,3,6,7,8-HxCDD 0.1 1,2,3,4,7,8-HxCDF 0.1

1,2,3,7,8,9-HxCDD 0.1 1,2,3,7,8,9-HxCDF 0.1

1,2,3,6,7,8-HxCDF 0.1

1,2,3,4,6,7,8-HpCDD 0.01 2,3,4,6,7,8-HxCDF 0.1

OCDD 0.001 1,2,3,4,6,7,8-HpCDF 0.1

1,2,3,4,7,8,9-HpCDF 0.01

OCDF 0.01

(T = tetra, P = penta, Hx = hexa, Hp = hepta, O = octa)

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PART 2

Categories of substances and preparations not specifically named in Part 1



of dangerous substances

Categories of dangerous substances as delivered in Article 3 (4),

for the application of


1. VERY TOXIC 5 20

2. TOXIC 50 200

3. OXIDIZING 50 200

4. EXPLOSIVE (where the substance orpreparation falls within the definition givenin Note 2 (a))

50 200

5. EXPLOSIVE (where the substance orpreparation falls within the definition givenin Note 2 (b))

10 50

6. FLAMMABLE (where the substance orpreparation falls within the definition givenin Note 3 (a))

5000 50,000

7 a. HIGHLY FLAMMABLE (where thesubstance or preparation falls within thedefinition given in Note 3 (b) (1)) 50 200

7b.

HIGHLY FLAMMABLE liquids (where thesubstance or preparation falls within thedefinition given in Note 3 (b) (2)) 5000 50,000

8. EXTREMELY FLAMMABLE (where thesubstance or preparation falls within thedefinition given in Note 3 (c))

10 50

9. DANGEROUS FOR THE ENVIRONMENTin combination with risk phrases:

(i) R50: Very toxic to aquatic organisms

(ii) R51:Toxic to aquatic organisms; andR53: May cause long term adverse effectsin the aquatic environment

200

500

500

2000

10. ANY CLASSIFICATION not covered bythose given above in combination with riskphrases:

(i) R14: Reacts violently with water(including R14/15)

(ii) R29: in contact with water, liberatestoxic gas

100

50

500

200

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NOTES

1. Substances and preparations are classified according to the following Directives (as amended) and their

current adaptation to technical progress: Council Directive 67/548/EEC of 27 June 1967 on the approximation of the laws, regulations and

administrative provisions relating to the classification, packaging and labelling of dangerous substances (b),

Council Directive 88/379/EEC of 7 June 1988 on the approximation of the laws, regulations andadministrative provisions of the Member States relating to the classification, packaging and labelling ofdangerous preparations (c),

Council Directive 78/631/EEC of 26 June 1978 on the approximation of the laws of the Member Statesrelating to the classification, packaging and labelling of dangerous preparations (pesticides) (d).

In the case of substances and preparations which are not classified as dangerous according to any of the aboveDirectives but which nevertheless are present, or are likely to be present, in an establishment and which possessor are likely to possess, under the conditions found at the establishment, equivalent properties in terms of

major-accident potential, the procedures for provisional classification shall be followed according to the relevantArticle of the appropriate Directive.

In the case of substances and preparations with properties giving rise to more than one classification , for thepurposes of this Directive the lowest thresholds shall apply.

For the purposes of this Directive, a list providing information on substances and preparations shall beestablished, kept up to date and approved by the procedure set up under Article 22.

2. An explosive means:

(a) (i) a substance or preparation which creates the risk of an explosion by shock, friction, fire or othersources of ignition (risk phrase R 2),

(ii) a pyrotechnic substance is a substance (or mixture of substances) designated to produce heat, light,sound, gas or smoke or a combination of such effects through non-detonating self-sustained

exothermic chemical reactions, or

(iii)an explosive or pyrotechnic substance or preparation contained in objects;

(b) a substance or preparation which creates extreme risks of explosion by shock, friction, fire or othersources of ignition (risk phrase R 3).

3. Flammable, highly flammable, and extremely flammable in categories 6, 7 and 8 mean:

(a) flammable liquids:

substances and preparations having a flash point equal to or greater than 21 C and less than or equal to55C (risk phrase R 10), supporting combustion;

(b) highly flammable liquids:

1. substances and preparations which may become hot and finally catch fire in contact with air at

ambient temperature without any input of energy (risk phrase R 17), substances which have a flash point lower than 55 C and which remain liquid under pressure,

where particular processing conditions, such as high pressure or high temperature, may createmajor-accident hazards;

2. substances and preparations having a flash point lower than 21 C and which are not extremelyflammable (risk phrase R 11, second indent);

(b

) OJ No. 196, 16. 8. 1967, p. l. Directive as fast amended by Directive 93/105/EC (OJ No. L 294, 30.

11. 1993, p. 2l).

(

c

) OJ No. L 187, 16. 7. 1988, p. 14.(d) OJ No. L 206, 29. 7. 1978, p. 13. Directive as fast amended by Directive 92/32/EEC (OJ No. L 154, 5. 6.

1992, p. 1).

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(c) extremely flammable gases and liquids:

1. liquid substances and preparations which have a flash point lower than 0 C and the boiling point (or,in the case of a boiling range, the initial boiling point) of which at normal pressure is less than orequal to 35 C (risk phrase R 12, first indent), and

2. gaseous substances and preparations which are flammable in contact with air at ambient temperatureand pressure (risk phrase R 12, second indent), whether or not kept in the gaseous or liquid stateunder pressure, excluding liquefied extremely flammable gases (including LPG) and natural gasreferred to in Part 1, and

3. liquid substances and preparations maintained at a temperature above their boiling point.

4. The addition of dangerous substances to determine the quantity present at an establishment shall be carriedout according to the following rule:

if the sum

q1/Q + q2/Q + q3/Q + q4/Q + q5/Q + ... >1,

where qx= the quantity of dangerous substances x (or category of dangerous substances) falling within Parts1 or 2 of this Annex,

Q = the relevant threshold quantity from Parts 1 or 2,

then the establishment is covered by the relevant requirements of this Directive.

This rule will apply for the following circumstances:

(a) for substances and preparations appearing in Part 1 at quantities less than their individual qualifyingquantity present with substances having the same classification from Part 2, and the addition ofsubstances and preparations with the same classification from Part 2;

(b) for the addition of categories 1, 2 and 9 present at an establishment together;

(c) for the addition of categories 3, 4, 5, 6, 7a, 7b and 8, present at an establishment together.

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Appendix 2.B An example calculation

2.B.1 Description of the establishment and the installations

An establishment contains five separate installations. The area of the establishment is rectangular

between the lower left point ($400 m, $200 m) and the upper right point (+300 m, +300 m). A

residential area is situated to the north of the establishment, at 400 m from its centre.

The installations, Ii, are listed in Table 2.B.1.

Table 2.B.1 Installations, Ii, present at the establishment

No Location Process

I1 (200, 200) Production installation inside a building, containing pure chlorine in anamount of 2100 kg at a process temperature of 35 C (vapour pressure at a

process temperature of 10 bar)

I2 (0, 0) Production installation outdoors. The installation contains various

flammable substances at different process conditions:

ethylene amount 200,000 kg liquid at $30 C (vapour pressure 20 bar)

ethane amount 100,000 kg gas at 80 C

butane amount 10,000 kggas at 30 C

propylene amount 10,000 kgliquid at $35 C (vapour pressure 1.75 bar)

propane amount 50,000 kgliquid at 80C (vapour pressure 31 bar)

I3 ($300,$150) Installation for storage of a 30% solution of hydrochloric acid in water. The

storage tank is situated outdoors and contains 1,500,000 kg solution at a

temperature of 25 C (partial vapour pressure Pi= 0.02 bar).

I4 (200, 100) The storage tank is connected to a process installation inside a building

where an amount of 300,000 kg of the 30% solution of hydrochloric acid in

water is p rocessed at a temperature of 100 C (liquid, partial vapour

pressure of Pi= 1.1 bar).

I5 ($300,$125) A process installation outdoors contains pure ammonia (gas, 12,000 kg), a60% solution of ammonia in water (9000 kg solution at 43 C, with a parti

vapour pressure Pi= 9.4 bar). In the installation petrol is used (1000 kg) a

a temperature of 150 C.

The layout of the plant and the residential area is shown in Figure 2.B.1.

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Figure 2.B.1 Layout of the plant and residential area, showing points closest to the installation

(A-C). Indicated are the locations (solid circle) of the installations (I.1-I.5) and the

locations (solid square) where the selection numbers are calculated. The locations

1, 2, 3, .. and A-C correspond with the points in Table 2.B.5.

2.B.2 Calculation of the indication number

2.B.2.1 Installation I1

Installation I1is a process installation (O1= 1) situated in a building (O2= 0.1). One substance,

chlorine, is p resent in a quantity Q of 2100 kg. As the vapour pressure of chlorine is more than 3

bar, O3= 10. Chlorine is a toxic substance; in the gas p hase at 25 C; LC50(rat, ihl, 1hr) = 293

ppm [SZW97]. The limit value is equal to G = 300 kg. Therefore, AT1= 7.


Installation I2is a process installation (O1= 1) situated outdoors (O2= 1). Five different

combinations of substances and process conditions are present, as shown in Table 2.B.2.

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Table 2.B.2 Combinations of substances and process conditions present at Installation I2

Substance Q O3 G AF Note

ethylene 200,000 kg 10 10,000 kg 200 1ethane 100,000 kg 10 10,000 kg 100 2

butane 10,000 kg 10 10,000 kg 10 3

propylene 10,000 kg 5.4 10,000 kg 5.4 4

propane 50,000 kg 10 10,000 kg 50 5

Notes:

1. Ethylene is a flammable substance having a vapour pressure greater than 3 bar under the

process conditions.

2. Ethane is a flammable substance in the gas phase under the process conditions.

3. Butane is a flammable substance in the gas phase under the process conditions.

4. Propy lene is a flammable substance. The vapour pressure of propylene, Pi, is equal to

1.75 bar at the p rocess temperature, Tp= $35 C. Therefore X = 4.5 !1.75 $3.5 = 4.4.

The boiling point, Tbp, is equal to $48 C. Therefore#= 1 and O3= 5.4.

5. Propane is a flammable substance having a vapour pressure greater than 3 bar under the

process conditions.


Installation I3is for storage (O1= 0.1) and situated outdoors (O2= 1). The amount of hydrogen

chloride present is 30% of 1,500,000 kg solution; Q = 450,000 kg. The substance, 30% solution

of hydrochloric acid in water, is a liquid. The partial vapour pressure of the dangerous substance,

hydrogen chloride, is Pi= 0.02 bar; therefore X = 0.02. The boiling point of the substance, 30%

solution of hy drochloric acid in water, is 57 C, so #= 0. As the resulting O3is less than the

minimum value, 0.1, O3= 0.1. Hydrogen chloride is a toxic substance and in the gas p hase at 25

C; LC50(rat, ihl, 1hr) = 3124 ppm [SZW97]. The limit value is equal to G = 3000 kg. Therefore

AT3= 1.5.


Installation I4is a process installation (O1= 1) and situated inside a building (O2= 0.1). The

amount of hydrogen chloride present is 30% of 300,000 kg solution; Q = 90,000 kg. The partial

vapor pressure of hydrochloric acid is Pi= 1.1 bar at Tp= 100 C. The factor X = 4.5 !1.1 $3.5

= 1.5. The boiling point of the substance, 30% solution of hydrochloric acid in water, is 57 C,

so #= 0 and O3= 1.5. The limit value is equal to G = 3000 kg. Therefore AT

4= 4.5.


Installation I5is a process installation (O1= 1) and situated outdoors (O2= 1). Three

combinations of substances and process conditions are present. Furthermore, ammonia is both

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toxic and flammable; both these hazards should be considered. The combinations of substances

and process conditions are shown in Table 2.B.3.

Table 2.B.3 Combinations of substances and process conditions present at Installation I5

Substance Q O3 G AF AT Note

ammonia, pure 12,000 kg 10 3,000 kg 40 1

ammonia, pure 12,000 kg 10 10,000 kg 12 1

ammonia, solution 5400 kg 10 3,000 kg 18 2

ammonia, pure 5400 kg 10 10,000 kg 5.4 2

petrol 1000 kg 10 10,000 kg 1 3

Notes:

1. Ammonia is a gas under the process conditions. The Limit value for the toxic substanceammonia is equal to 3000 kg since ammonia is a gas at 25 C and LC50(rat, inh.,1hr) =

11,590 mg m-3[SZW97]. The limit value for the flammable substance ammonia is equal to

10,000 kg.

2. The quantity of ammonia present in solution is equal to 60% of 9000 kg solution, Q =

5400 kg. As the p artial vapour p ressure exceeds 3 bar, then O3= 10. The limit value for the

toxic substance ammonia is equal to 3000 kg since ammonia is a gas at 25 C and LC50(rat,

inh.,1hr) = 11,590 mg m-3[SZW97]. The limit value for the flammable substance ammonia

is equal to 10,000 kg.

3. Petrol is a flammable substance. The process temperature is higher than the 10% point. The

vapour pressure at 150 C has to be determined. For the example we assume it to be greater

than 3 bar. Therefore O3= 10.

2.B.2.6 S ummary

The result of calculating the indication number is summarised in Table 2.B.4.

The indication numbers are:

installation I1 AT= 7

installation I2 AF= 365

installation I3 AT= 1.5

installation I4 AT= 4.5

installation I5 AT= 58, AF= 18.4

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Table 2.B.4 Indication numbers of the installations

Inst. Substance Type O1 O2 O3 Q G Ai

I1 chlorine T 1 0.1 10 2100 kg 300 kg 7I2 ethylene F 1 1 10 200,000 kg 10,000 kg 200

ethane F 1 1 10 100,000 kg 10,000 kg 100

butane F 1 1 10 10,000 kg 10,000 kg 10

propylene F 1 1 5.4 10,000 kg 10,000 kg 5.4

propane F 1 1 10 50,000 kg 10,000 kg 50

I3 30%-HCl T 0.1 1 0.1 450,000 kg 3000 kg 1.5

I4 30%-HCl T 1 0.1 1.5 90,000 kg 3000 kg 4.5

I5 ammonia (g) T 1 1 10 12,000 kg 3000 kg 40

ammonia (s) T 1 1 10 5400 kg 3000 kg 18

ammonia (g) F 1 1 10 12,000 kg 10,000 kg 12

ammonia (s) F 1 1 10 5400 kg 10,000 kg 5.4petrol F 1 1 10 1000 kg 10,000 kg 1

2.B.3 Calculation of the selection number

The selection number has to be calculated for points on the site boundary and residential area.

There are 48 points selected at 50-m intervals along the boundary (see Figure ). Furthermore, for

each installation the point in the plant area closest to the installation is selected. The selection

number is calculated from the distance of each point to the installation (minimal 100 metres). The

results are shown in Table 2.B.5. Installations 1, 2 and 5 have been selected for a QRA.

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Table 2.B.5 Selection numbers at the positions selected

No. x y S1 S2 S3 S4 S5T

S5F

Selected

1 25 300 1.7 13.4 0.0 0.6 2.0 0.1 22 75 300 2.7 12.3 0.0 0.8 1.8 0.1 23 125 300 4.5 10.6 0.0 1.0 1.6 0.1 24 175 300 6.6 8.7 0.0 1.1 1.4 0.1 1, 25 225 300 6.6 6.9 0.0 1.1 1.3 0.1 1, 26 275 300 4.5 5.4 0.0 1.0 1.1 0.0 1, 27 300 275 4.5 5.4 0.0 1.1 1.1 0.0 1, 28 300 225 6.6 6.9 0.0 1.8 1.2 0.1 1, 29 300 175 6.6 8.7 0.0 2.9 1.3 0.1 1, 2

10 300 125 4.5 10.6 0.0 4.2 1.4 0.1 211 300 75 2.7 12.3 0.0 4.2 1.5 0.1 212 300 25 1.7 13.4 0.0 2.9 1.5 0.1 213 300 $25 1.2 13.4 0.0 1.8 1.6 0.1 214 300 $75 0.8 12.3 0.0 1.1 1.6 0.1 2

15 300 $125 0.6 10.6 0.0 0.7 1.6 0.1 216 300 $175 0.5 8.7 0.0 0.5 1.6 0.1 217 275 $200 0.4 9.3 0.0 0.5 1.7 0.1 218 225 $200 0.4 13.4 0.1 0.5 2.1 0.1 219 175 $200 0.4 19.4 0.1 0.5 2.5 0.2 220 125 $200 0.4 27.8 0.1 0.5 3.1 0.2 221 75 $200 0.4 37.5 0.1 0.4 4.0 0.3 222 25 $200 0.4 44.6 0.1 0.4 5.2 0.5 223 $25 $200 0.3 44.6 0.2 0.3 7.1 0.8 224 $75 $200 0.3 37.5 0.3 0.3 10.3 1.3 225 $125 $200 0.3 27.8 0.5 0.2 16.0 2.6 2, 526 $175 $200 0.2 19.4 0.8 0.2 27.3 5.8 2, 527 $225 $200 0.2 13.4 1.5 0.2 51.6 15.1 528 $275 $200 0.2 9.3 1.5 0.1 58.0 18.0 529 $325 $200 0.2 6.6 1.5 0.1 58.0 18.0 530 $375 $200 0.1 4.8 1.5 0.1 51.6 15.1 531 $400 $175 0.1 4.4 1.4 0.1 46.4 12.9 532 $400 $125 0.2 5.0 1.4 0.1 58.0 18.0 533 $400 $75 0.2 5.4 1.0 0.1 46.4 12.9 534 $400 $25 0.2 5.7 0.6 0.1 29.0 6.4 535 $400 25 0.2 5.7 0.4 0.1 17.8 3.1 536 $400 75 0.2 5.4 0.2 0.1 11.6 1.6 537 $400 125 0.2 5.0 0.2 0.1 8.0 0.9 2, 538 $400 175 0.2 4.4 0.1 0.1 5.8 0.6 2, 539 $400 225 0.2 3.8 0.1 0.1 4.4 0.4 2, 540 $400 275 0.2 3.2 0.1 0.1 3.4 0.3 2, 541 $375 300 0.2 3.3 0.1 0.1 3.1 0.2 2, 5

42 $325 300 0.2 4.2 0.1 0.1 3.2 0.2 2, 543 $275 300 0.3 5.4 0.1 0.2 3.2 0.2 2, 544 $225 300 0.4 6.9 0.1 0.2 3.1 0.2 245 $175 300 0.5 8.7 0.1 0.2 3.0 0.2 246 $125 300 0.6 10.6 0.1 0.3 2.7 0.2 247 $75 300 0.8 12.3 0.1 0.4 2.5 0.2 248 $25 300 1.2 13.4 0.1 0.5 2.3 0.1 2C 200 400 1.8 1B 0 400 5.7 2A $300 400 0.0C 200 400 0.5A $300 400 2.1 0.12 5

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Appendix 2.C Commentary

The procedure to select installations for the QRA is largely based on the references [IPO],

[KO 9], [KO 12], [KO 19-2] and [NR].

In addition, the following changes are made:

Section 2.2 describes the criteria to exclude particular substances from the QRA

calculations. Article 9, Paragraph 6 of Council Directive 96/82/EC indicates that particular

substances in a state incapable of creating a major-accident hazard can be excluded from the

Safety Report [EU96]. The criteria to be used are given in the Commission decision on

harmonized criteria for dispensations according to Art icle 9 of Council Directive 96/82/EC

of 9 December 1996 on the control of major-accident hazards involving dangerous

substances [EU98]. Consequently, it has been decided to exclude these substances from the

QRA calculations using the same criteria.

Section 2.3.2.1 records the rule on whether mixtures and preparations of toxic substances

need to be considered. This rule has been changed. Previously, dangerous substances in

concentrations less than 5% did not need to be considered. This rule is now replaced by the

limits of the corresponding EU directives [EU88].

To facilitate QRA calculations in case many different substances are stored at different

times, the use of sample substances has been added in Section 2.3.2.1.

The factor O3

accounts for the process conditions and is a measure of the amount of

substance in the gas phase after the release (see Section 2.3.2.2.3). In the calculation of O3,

an amount #is used to account for the extra evaporation due to the heat flux from the

environment to the liquid pool formed. The use of the amount #deviates from the

calculations used previously [P 172, IPO]. In [P 172, IPO], the amount #is only added if

the process temperature is lower than the ambient temperature. This condition is omitted

here for two reasons:

the addition of an amount #is meant to account for the extra evaporation caused by the

heat flux of the environment to the liquid pool. Therefore it is more reasonable to have

the value of #not dependent on the process temperature, but only on the difference

between the atmosp heric boiling point and the (fixed) ambient temperature.

In practice, this condition is likely not to be tested. The saturation pressure at p rocesstemperature for most substances will be higher than 3 bar if the process temperature is

equal to or higher than 25 C and the atmospheric boiling point is lower than $25 C. A

saturation pressure at a process temperature higher than 3 bar already results in the

maximum value of X = 10.

For substances in the liquid phase, a factor X is used to calculate the factor O3(see Section

2.3.2.2.3). The use of an interpolation for the factor X between 1 and 10 has not

previously been clearly described for dangerous substances in non-dangerous solvents. The

interpolation is introduced here to be more in line with pure substances.

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The calculation of the limit value, G, has been copied from [SZW97] (see Section 2.3.2.3).

One modification is made: [SZW97] assigns a limit value of 1 kg to substances which are

extremely toxic. Therefore a number of carcinogenic substances have a limit value of 1 kg,

although acute effects are not known. Since the QRA is directed to short-term lethal effects,the category of extremely toxic substances is no longer included.

The selection method for large inter-unit pipelines represents a new procedure not

previously described. The two-phase outflow is calculated using PHAST V5.2 [DNV98].

The outflow is calculated for a pipeline connected to a large spherical vessel at a height of

one metre. The mass of the pressurized liquefied gas in the vessel is equal to 500 ton, the

filling grade is 0.9 and temperature T = 282 K. The length of the pipeline emptied in 600

seconds is determined iteratively. First, a pipeline length is postulated. Next, the mass

released in 600 seconds following a rupture of the pipeline is calculated. Finally, the volume

corresponding to the mass released and the p ipeline length corresponding with this volume

is calculated. Using the new pipeline length, the procedure is repeated until convergenceoccurs.

Appendix 2.A describes to procedure to assess the obligation to make a Safety Report. The

procedure is taken from [EU96]. The note describing the presence of a substance in step 1

is not stated in [EU96] but taken from [KO 12].

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LOCs 3.1

3. LOSS OF CONTAINMENT EVENTS

3.1 Introduction

This chapter describes the Loss of Containment events (LOCs) that need to be included in the

QRA for establishments. The complete set of LOCs consists of generic LOCs, external-impact

LOCs, loading and unloading LOCs and specific LOCs.

Generic LOCs

The generic LOCs cover all failure causes not considered explicitly, like corrosion, construction

errors, welding failures and blocking of tank vents.

External-impact LOCs

LOCs for external impact are considered explicitly for transport units. The external-impact LOCs

applying to stationary installations and pipelines are assumed to be either already included in thegeneric LOCs or should be included by adding an extra failure frequency.

Loading and unloading LOCs

Loading and unloading LOCs cover the t ranshipment of material from transport units to

stationary installations and vice versa.

Specific LOCs

Specific LOCs cover the LOCs specific to the process conditions, process design, materials and

plant layout. Examples are runaway reactions and domino effects.

Only LOCs that contribute to the individual and/or societal risk should be included in the QRA.

This means that LOCs of an installation should be included only if two conditions are fulfilled:

i.e. (1) frequency of occurrence is equal to or greater than 10-8per year and (2) lethal damage (1%

probability) occurs outside the establishments boundary or the transport route.

The LOCs for establishments are described in Sections 3.2.1 - 3.2.9.

3.2 Loss of Containment events at establishments

Loss of Containment events (LOCs) are defined for various systems in an establishment. Thesystems and their LOCs are described in more detail in the sections as indicated in Table 3.1.

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LOCs 3.2

Table 3.1 LOCs for systems in an establishment

System Section

Stationary tanks and vessels, pressurised 3.2.1Stationary tanks and vessels,atmospheric

3.2.2

Gas cylinders 3.2.1Pipes 3.2.3Pumps 3.2.4Heat exchangers 3.2.5Pressure relief devices 3.2.6Warehouses 3.2.7Storage of explosives 3.2.8Road tankers 3.2.9Tank wagons 3.2.9Ships 3.2.9

3.2.1 Stationary pressurised tanks and vessels

Of the various types of pressurised stationary tanks and vessels, pressure, process and reactor

vessels can be distinguished. These are described below.

Pressure vessel

A pressure vessel is a storage vessel in which the pressure is (substantially) more than 1 bar

absolute.

Process vesselIn a process vessel a change in the physical properties of the substance occurs, e.g. temperature

or phase. Examples of process vessels are distillation columns, condensers and filters. Vessels

where only the level of liquid changes can be considered as pressure vessels.

Reactor vessel

In reactor vessels a chemical change of the substances occurs. Examples of reactor vessels are

batch and continuous reactors. A vessel where a strong exothermic mixing of substances occurs

should also be considered as a reactor vessel.

The LOCs for p ressure, p rocess and reactor vessels are given in Table 3.2, the failure frequencies

of these LOCs for stationary vessels inTable 3.3.

Table 3.2 LOCs for stationary vessels

LOC for stationary vessels

G.1 Instantaneous release of the complete inventory

G.2 Continuous release of t he complete inventory in 10 min at a constant rate of release

G.3 Continuous release from a hole with an effective diameter of 10 mm

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LOCs 3.3

Table 3.3 Frequencies of LOCs for stationary vessels

Installation (part) G.1

Instantaneous

G.2

Continuous,

10 min

G.3

Continuous,

!10 mm

pressure vessel 5 "10-7

y-1

5 "10-7

y-1

1 "10-5

y-1

process vessel 5 "10-6

y-1

5 "10-6

y-1

1 "10-4

y-1

reactor vessel 5 "10-6

y-1

5 "10-6

y-1

1 "10-4

y-1

Notes:

1. A vessel or tank consists of the vessel (tank) wall and the welded stumps, mounting plates

and instrumentation pipes. The LOCs cover the failure of the tanks and vessels and the

associated instrumentation pipework. The failure of pipes connected to the vessels and

tanks should be considered separately (see Section 3.2.3).

2. The failure frequencies given here are default failure frequencies based on the situation that

corrosion, fatigue due to vibrations, operating errors and external impacts are excluded. A

deviation of the default failure frequencies is p ossible in sp ecific cases. A lower failure frequency can be used if a tank or vessel has special provisions

additional to the standard provisions, e.g. according to the design code, which have an

indisputable failure-reducing effect. However, the frequency at which the complete

inventory is released (i.e. the sum of the frequencies of the LOCs, G.1 and G.2) should

never be less than 1 "10-7per year.

A higher frequency should be used if standard provisions are missing or under

uncommon circumstances. If external impact or operating errors cannot be excluded, an

extra failure frequency of 5 "10-6per year should be added to LOC G.1,

Instantaneous and an extra failure frequency of 5 "10-6per year should be added to

LOC G.2, Continuous, 10 min.

3. Vessels and tanks can be (partly) in-ground, or situated inside or outside a building. The

LOCs and their frequencies are not dependent on the situation. The modelling of a release

inside a building is described in Chapter 4.

4. Storage tanks can be used for the storage of different substances at different t imes. If large

numbers of different substances are transhipped from an establishment, it is useful to

classify the substances and use sample substances for each category in the QRA. A

classification method is described in [VVoW95]. It should be noted that if a specific

substance makes up an important p art of the total amount t ranshipped, the substance itself

will have to be used in the calculation.

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LOCs 3.4

5. Storage tanks may have a pressure just above 1 bar absolute. These tanks have to be

considered as atmospheric storage tanks. Examples are cryogenic tanks and atmospheric

storage tanks with nitrogen blanketing.

6. The potential consequences of simultaneous failure of more than one tank should be

considered. For instance, if several tanks are located close to each other, a BLEVE of one

tank may lead to the failure of several other tanks. If several tanks are located in one bund,

the capacity of the bund should be sufficient to contain the liquid of all tanks, otherwise

simultaneous failure of more than one tank may lead to a sp ill outside the bund.

7. Failure frequencies of process and reactor vessels are higher by a factor of 10 than the

failure frequencies of pressure vessels. This factor covers the hazards imposed by the

chemical process, like runaway reactions unidentified in the analysis of the process.

However, the process is assumed to be analysed using methods like HAZOP, what/if and

checklist analyses and appropriate measures are taken to prevent the hazards identified. Amore complete description of analysis methods is given in the Red Book [CPR12E].

8. Catastrophic failure of a gas cylinder does not generally lead to lethal effects outside the

establishment. However, the possibility of domino effects should be considered, e.g.

following catastrophic failure of a gas cylinder with acetylene. The frequency of

catastrophic failure of a gas cylinder (instantaneous release) is 1 "10-6per year.

3.2.2 Stationary atmospheric tanks and vesse ls

The various types of stationary tanks and vessels can be distinguished as given below:

Single-containment atmospheric tank

A single-containment atmospheric tank consists of a primary container for the liquid. An outer

shell is either present, or not, but when present, primarily intended for the retention and

protection of insulation. It is not designed to contain liquid in the event of the primary

containers failure.

Atmospheric tank with a protective outer shell

An atmospheric tank with a protective outer shell consists of a primary container for the liquid

and a protective outer shell. The outer shell is designed to contain the liquid in the event of failure

of the primary container but is not designed to contain any vapour. The outer shell is notdesigned to withstand all possible loads, e.g. explosion (static pressure load of 0.3 bar during 300

ms), penetrating fragments and cold (thermal) load.

Double-containment atmospheric tank

A double-containment atmospheric tank consists of a primary container for the liquid and a

secondary container. The secondary container is designed to contain the liquid in the event of

failure of the primary container and to withstand all possible loads, like explosion (static pressure

load of 0.3 bar during 300 ms), penetrating fragments and cold (thermal) load. The secondary

container is not designed to hold any kind of vapour.

Full-containment atmospheric tank

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LOCs 3.5

A full-containment atmospheric tank consists of a primary container for the liquid and a

secondary container. The secondary container is designed to contain both the liquid and vapour in

the event of failure of the primary container, and to withstand all possible loads, like explosion

(static pressure load of 0.3 bar during 300 ms), penetrating fragments and cold. The outer roof issupported by the secondary containment and designed to withstand loads e.g. explosion.

Membrane tank

A membrane tank consists of a primary and a secondary container. The primary container is

formed by a non-self-supporting membrane that holds the liquid and its vapour under normal

operating conditions. The secondary container is concrete and supports the primary container.

The secondary container has the capacity to contain all the liquid and to realise controlled venting

of the vapour if the inner tank fails. The outer roof forms an integral part of the secondary

containment.

In-ground atmosp heric tankAn in-ground atmospheric tank is a storage tank in which the liquid level is at or below ground

level.

Mounded atmospheric tank

A mounded atmospheric tank is a storage tank that is completely covered with a layer of soil and

in which the liquid level is above ground level.

The LOCs for atmosp heric tanks are given in Table 3.4 and the frequencies of these LOCs in

Table 3.5.

Table 3.4 LOCs for atmospheric tanks

LOCs for atmospheric t anks

G.1 Instantaneous release of the complete inventory

a directly to the atmosphere

b from the primary container int o the unimpaired secondary container or outer shell

G.2 Continuous release of the complete inventory in 10 min at a constant rate of release



G.3 Continuous release from a hole with an effective diameter of 10 mm



Full-containment atmospheric tank

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LOCs 3.6

Table 3.5 Frequencies of LOCs for atmospheric tanks

Installation (part) G.1a

Instantan.

release to

atmosphere

G.1b

Instantan.

release to

secondary

container

G.2a

Continuous

10 min

release to

atmosphere

G.2b

Continuous

10 min

release to

secondary

container

G.3a

Continuous

!10 mm

release to

atmosphere

G.3b

Continuous

!10 mm

release to

secondary

container

single-

containment tank 5 "10-6y

-15 "10

-6y

-11 "10

-4y

-1

tank with a

protective outer

shell 5 "10-7y-1 5 "10-7y-1 5 "10-7y-1 5 "10-7y-1 1 "10-4y-1

double

containment tank 1.25 "10-8y

-15 "10

-8y

-11.25 "10

-8y

-

1

5 "10-8y

-11 "10

-4y

-1

full containment

tank 1 "10-8y

-1

membrane tank see note 7

in-ground tank 1 "10-8y

-1

mounded tank 1 "10-8y

-1

Notes:

1. A vessel or tank consists of the vessel (tank) wall and the welded stumps, mounting plates

and instrumentation pipes. The LOCs cover the failure of the tanks and vessels, and the

associated instrumentation pipework. The failure of pipes connected to the vessels and

tanks should be considered separately (see Section 3.2.3).

2. Tanks can be situated inside or outside a building. The LOCs are not dependent on thesituation. Modelling a release inside a building is described in Chapter 4.

3. Storage tanks can be used for storing different substances at different times. If large

numbers of different substances are transhipped from an establishment, it is useful to

classify the substances and use sample substances for each category in the QRA. A

classification method is described in [VVoW95]. It should be noted that if a specific

substance constitutes an important part of the total amount transhipped, the substance

itself will have to be used in the calculation.

4. A cryogenic tank is an atmospheric tank with a storage temperature below ambient

temperature. The LOCs for a cryogenic tank are the LOCs of the corresponding type of

atmospheric storage tank.

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LOCs 3.7

5. Atmospheric storage tanks may have a pressure just above 1 bar absolute. These tanks

should be considered as atmospheric storage tanks. Examples are cryogenic tanks and

atmospheric storage tanks with nitrogen blanketing.

6. The potential consequences of simultaneous failure of more than one tank should be

considered. For instance, if several tanks are located in one bund, the capacity of the bund

should be sufficient to contain the liquid of all tanks, otherwise simultaneous failure of

more than one tank may lead to a spill outside the bund.

7. The failure frequency of a membrane tank, determined by the strength of the secondary

container, should be estimated case by case using the data on the other types of

atmospheric tanks.

8. The liquid level in an in-ground atmospheric tank is at or below ground level. The

surrounding soil should be considered as a secondary container; failure of the tank results inflash and pool evaporation only.

3.2.3 Pipes

The LOCs for pipes cover all types of process pipes and inter-unit pipelines above ground of an

establishment. The LOCs for transport pipelines underground are given elsewhere. The LOCs for

pipes are given in Table 3.6 and LOC frequencies for pipes in Table 3.7.

Table 3.6 LOCs for pipes

LOCs for pipes

G.1 Full bore rupture- outflow is from both sides of the full bore rupture

G.2 Leak - outflow is from a leak with an effective diameter of 10% of the

nominal diameter, a maximum of 50 mm

Table 3.7 Frequencies of LOCs for pipes

Installation (part) G.1

Full bore rupture

G.2

Leak

pipeline,nominal diameter < 75 mm 1 "10

-6m-1y -1 5 "10-6m-1y-1

pipeline,75 mm #nominal diameter #150mm

3 "10-7m-1y -1 2 "10

-6m-1y-1

pipeline,nominal diameter > 150 mm 1 "10-7

m-1

y-1

5 "10-7

m-1

y-1

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LOCs 3.8

Notes:

1. The figures given for the pipework failure rate are based on process p ipework operating in

an environment where no excessive vibration, corrosion/erosion or thermal cyclic stressesare expected. If there is

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